Pre-development exposure assembly

ABSTRACT

A pre-development exposure assembly is provided within an electrostatic reproduction machine transverse to the photoconductive surface thereof to selectively expose side portions of the photoconductive surface in response to a signal generated by a switch associated with the paper supply assembly responsive to paper size therein.

vO Umted States Patent 1 1 1111 3,809,472 Liechty [45] M 7, 1974PRE-DEVELOPMENT EXPOSURE 3,685,894 8/1972 Lux et a1 355/3 ASSEMBLY3133155; 13/1325 81*? 322132;

, ar 1 lnvemori Karl y, Pittsford, 3,122,455 2/1964 Grimm et a1 355/3 xAssigneez xerox Corporation, Stamford 3556.655 l/1971 Lux et a1 355/51 XConn. Primary ExaminerRobert P. Greiner [22] Flled: 1971 Attorney,Agent, or Firm lames J. 'Ralabate [21] Appl. No.: 214,244

' [57] ABSTRACT [52] US. Cl 355/3 R, 355/16, 355/125 [51 Int. Cl. G03b15/00 Predevelopmem .exposure assembly provlded [58] Field of Search355/3 14 16 7 74 125 wlthm an electrostanc reproducnon machme trans- 5verse to the photoconductive surface thereof to selectively expose sideportions of the photoconductive sur- 56] References Cited face inresponse to a signal generated by a switch associated with the papersupply assembly responsive to I UNITED STATES PATENTS paper Sizetherein. 3,687,538 8/1972 Matsumoto 355/3 3,724,940 4/1973 Koizumi 355/35 Claims, 3 Drawing Figures T 42 a; 52 a 3- 5:-) 56 u 50 i (=3? E H \J VV 58 (i 1 k c. 4

1 PRE-DEVELOPMENT EXPOSURE ASSEMBLY BACKGROUND OF THE INVENTION Thisinvention relates to electrostatography, and more particularly toimprovements in the control of development' with particulate tonermaterial that is adapted for use in electrostatographic apparatus.

In the practice of xerography as described in U.S. Pat. No. 2,297,691 toChester F. Carlson, a xerographic surface comprising a layer ofphotoconductive insulating material affixed to a conductive backing isused to support electrostatic images. In the usual method of carryingout the process, the xerographic plate is electrostatically chargeduniformly over its surface and then exposed to a light pattern of theimage being reproduced to thereby discharge the charge in the areaswhere light strikes the layer. The undischarged areas of the layer .thusform an electrostatic charge pattern in conformity with theconfiguration of the original light pattern.

The latent electrostatic image may then be developed by contacting itwith a finely divided electrostatically attractable material, such as aresinous powder; The powder is held in the image areas by theelectrostatic fields on the layer. Where the field is greatest, thegreatest amount of material is deposited; and where the field is least,little or no material is deposited. Thus, a powder image is produced inconformity with the light image of the copy being reproduced. The powderis subsequently transferred to a sheet of ,paper or other surface andsuitably affixed to thereby form a permanent print. i

The latest machine concept for copiers utilizes flash exposure of adocument and the arrangement ofa mov-' ing photoconductor materialin'the form of an endless belt. Additionally, the photoconductivesurface of such a machine is continuously charged. In order toeffectively develop the latent image produced in such machine with theprovision for solid area coverage, a developing system is employed whichsupplies toner particles in relatively large quantities. Additionally,high production rates are more readily achievable by passing the imagereceiving member sideways through the transfer and fixing stations asdistinguished from length-wise transit as performed by most prior artdevices, e.g. line copy would be parallel to the direction of rotationof the photoconductive belt.

Such high-speed machines are also being provided with image reducingcapabilities. Exposure of a translucent document on a platen to bereproduced in reduced size, results in unexposed planes on each side ofthe photoconductive surface, assuming alignment of the document asdistinguished from edge alignment on the machine. Such planes, afterpassage through a solid area developing station, would contain a'highconcentration of toner particles, i.e in effect, a'developed solid areaimage, although not in response to exposure of such area imagewise tolight of an image to be reproduced. If the photoconductive belt ispassed through a transfer station in contact with an image receivingmember ofa length equal to the original document, the top and bottom ofthe receiving member will have a margin of .solid area coverage. If thereceiving member is of a length corresponding to the length of thereduced image or less, the toner particles will pass through suchstation, with a portion adhering to the OBJECTS OF THE INVENTION It isan object of this invention to improve electrostatic reproductionmachines for effecting high speed development of line copy and solidarea with minimum waste of developing material.

Another object of this invention is to permit continuous operation of anelectrostatic charging device in an electrostatic reproduction machinethereby allowing the high speed operation thereof.

SUMMARY OF THE INVENTION These and other objects of the invention areobtained by a pre-development exposure assembly disposed transverse to aphotoconductive surface. The predevelopment exposure assembly isprovided with pairs of cooperating slits and a discharge devicepositioned within the assembly and associated with each pair of slitsfor selective discharging of a moving photoconductor surface prior todevelopment of an electrostatic latent image thereon. A control circuitis associated with each discharge device and is arranged to control theenergization thereof in response to a signal generated by theinteraction between a reduced magnification mode and a switch providedon a paper assembly actuated in response tothe length of paper thereon.The energization of the respective discharge devices dissipates thecharged areas along selective areas on the photoconductive surface notexposed imagewise to a light pattern as hereinbelow discussed.

DESCRIPTION OF THE DRAWINGS A better understanding of the presentinvention as well as other objects and further features thereof willbecome apparent upon consideration of the following detailed disclosurethereof, especially when taken with the accompanying drawings, whereinlike numerals designate like parts throughout.

FIG. 1 is a schematic sectional view of an electrostatic reproductionmachine embodying the principles of the invention;

FIG. 2 is a plane view of the pre-development exposure assembly;

FIG. 3 is a cross-sectional view of the predevelopment exposure assemblytaken along the lines of 3-3 of FIG. 2.

For a general understanding of the illustrated copier/reproductionmachine in which the invention may be incorporated, reference is had toFIG. 1 in which the various system components for the machine areschematically illustrated. A document D to be cop- .ied is placed upon atransparent support platen P belt 12 arranged on a belt'assembly,generally indicated by the reference numeral 14.

The belt 12 comprises a photoconductive layer of selenium which is thelight receiving surface and imaging medium for the apparatus, on aconductive backing. The surface of the photoconductive belt is madephotosensitive by a previous step of uniformly charging the same bymeans of a corona generating device or corotron 13.

The belt is journaled for continuous movement upon three rollers 20, 21and 22 positioned with their axes in parallel. The photoconductive beltassembly 14 is slidably mounted upon two support shafts 23 and 24 withthe roller 22 rotatably supported on the shaft 23 which is secured tothe frame of the apparatus and is rotatably driven by a suitable motorand drive assembly (not shown) in the direction of the arrow at aconstant rate. During exposure of the belt 12, the portion exposed isthat portion of the belt running between rollers and 21. During suchmovement of the belt 12, the reflected light image of such originaldocument positioned on the platen is flashed on the surface of the beltto produce an electrostatic latent image thereon at exposure station A.

As the'belt surface continues its movement, the electrostatic imagepasses through a developing station B in which there is positioned adeveloper assembly generally indicated by the reference numeral 15, andwhich provides development of the electrostatic image by means ofmultiple brushes 16 as the same moves through the development zone.

The developed electrostatic image is transported by the'belt to atransfer station C whereat a sheet of copy paper is moved between atransfer roller and the belt at a speed in synchronism with the movingbelt in order to accomplish transfer of the developed image solely by anelectrical bias on the transfer roller. There is provided at thisstation a sheet transport mechanism generally indicated at 17 adapted totransport sheets of paper from a paper handling mechanism generallyindicated by the reference numeral l8'to the developed image on the beltat the station C.

After the sheet is stripped from the belt 12, it is conveyed into afuser assembly, generally indicated by the reference numeral 19, whereinthe developed and transferred xerographic powder image on the sheetmaterial is permanently affixed thereto. After fusing, the finished copyis discharged from the apparatus at a suitable point for collectionexternally of the apparatus.

Further details regarding the structure of the belt assembly l4 and itsrelationship with the machine and support therefor may be found in thecopending Application Ser. No: 102,312 filed Dec. 29, 1970 assigned tothe same assignee, now U.S. Pat. No. 3,730,623, issued May 1, 1973.

The predevelopment exposure assembly of the present invention, generallyindicated as 30, is positioned within the lower portion of thereproduction machine between the exposure station A and the developingstation B, as illustrated in FIG. 1. Referring now to FIGS. 2 and 3, thepre-development assembly is comprised of a molded housing 32, a base 34and discharge devices, such as fluorescent lamps 36'and 38 activated bya conventional energizing means (not shown).. The housing 32 is formedwith a top wall 40, side walls 42 and 44, and end walls 46 and 48.Within the housing 32, there is provided an intermediate wall 50 formingchambers 52 and 54 in which fluorescent lamps 36 and 38, respectivelyare disposed. The top wall 40 of the housing 32 is formed with pairs ofcooperating slits 56 and 58 which permit the passage of actinicradiation therethrough from fluorescent lamps 36 and38, respectively.The pre-development exposure assembly 30 is provided with a bracketmeans, generally indicated as 60, for mounting the assembly 60' withinthe electrostatic machine. i

Each of the fluorescent lamps 36 and 38 may be provided with a controlcircuit the numeral 62, such as described in copending application Ser.No. 145,013, tiled May 19, 1971, whichis a continuation of applicationSer. No. 73l,967, filed May 24, 1968, now abandoned, filed by James M.Donohue, entitled SELEC- TIVE DEVELOPMENT CONTROL FOR ELECTRO- STATICREPRODUCTION MACHINES, each of which control circuits being energized bya signal from a switch the numeral 64 provided on the paper supplyelevator assembly, as described in copending application Ser. No.214,345 filed Dec. 30, 1971 by Sission, et al relating to paperdimension sensing. The control circuits may also be energized by anoperator through a reduced magnification mode of the machine.

In operation of a copier/reproduction machine, as hereinabove described,the endless photoconductive belt is continuously charged, for example,by corona charging from a coronode array, such as disclosed in U. S.Pat. No. 2,588,698 to Carlson. If in one mode, for example, the maximumdimension of paper in the supply assembly correspondsto that of thedocument to be copied, neither of the control circuits associated withthe respective fluorescent lamps will be energized.

Should a signal be developed by a switch disposed on the supplyassembly; sensing that the supply paper is of smaller dimension than thedesigned maximum dimension of the supply assembly, a correspondingcontrol system is energized thereby illuminating the respectivefluorescent lamp to expose continuously the side portions (i.e.cylindrical planes at the roller 21) of the photoconductive surfacecorresponding to an area determined by the width of the pair of slitsthrough which the light passes. Alternatively, a fluorescent lamp may beactivated in response to a signal indicative of a reduced magnificationmode of the machine by the depression by an operator of an appropriateselection device. I

It will be appreciated that in the absence of such exposure, thatdeveloper particles will adhere to planes on the sides of thephotoconductive surface. There being no image receiving surface ofsufficient dimension at the transfer station D, some of the tonerparticles will attach .to the transfer roller with the subsequentrequirementof transfer roller cleanup, while the remaining portion ofthe toner particles adhering to the belt will be removed by a tonerclean-up brush, such as illustrated as 26 in FIG. 1. Thus without thepresent invention, it can be readily appreciated that excessive stepsmust be taken to provide for toner clean-up within such acopier/reproduction machine thereby presenting a serious solids handlingproblem, with a concomitant excessive consumption of toner particles.

While the present invention has been described with reference to theincorporation of two pairs of slits in .the pre-development exposureassembly, it will be understood that one, or three or more slits may bepro- 'ing slits at one end thereof instead of at both ends dependent'onthe reference positioning of the document on the platen as well as theoptic system to be employed in the machine. The principle of the presentinvention, while discussed with reference to a high speed machineemploying an endless photoconductive belt being continuously charged, isapplicable to high-speed drumtype electrostatographic machinesregardless of the orientation in which the receiving members aretransported therethrough. Discharge devices, other than fluorescentlamps may be employed in the present invention, e.g. corotrons, and thelike.

While the instant invention as to its objects and advantages has beendescribed herein as carried in specific embodiments thereof, it is notdesired to be limited thereby, but it is intended to cover the inventionbroadly within the scope of the appended claims.

What is claimed is:

1. In an electrostatic reproduction machine havinga movingphotoconductive surface adapted to be charged and to carry anelectrostatic latent image thereon, and developing means positioned at adevelopment zone to develop the moving electrostatic image on saidsurface, the developed-image being adapted for transfer to a suitablereceiving member, the combination comprising:

a discharge device adapted when activated to discharge a charged area ona side portion of said surface, said device being positioned todischarge portions of said surface prior to development thereof;

meansadapted on a control signal to actuate said discharge device; andcontrol means responsive to the size of the receiving member operativeon a predetermined receiving member size to provide said control signalwhereby said discharge "device is activated to remove the charge on theside portion of said surface extending beyond the edges of saidreceiving member.

2, In the electrostatic reproduction machine as defined in claim 1wherein said device discharges charged areas on either side portions ofsaid photoconductive surface.

3. The electrostatic reproduction machine as defined in claim 1 whereinsaid discharge means is a fluorescent lamp.

4. In an electrostatic reproduction machine having a movingphotoconductive surface adapted to be charged and to carry anelectrostatic latent image thereon, and developing means positioned at adevelopment zone to develop the moving electrostatic image on saidsurface, the developed image being adapted for transfer to a suitablereceiver member, the combination comprising:

means to provide an uncharged strip along the edge portion of 'saidsurface prior to development thereof;

means adapted to a control signal to actuate said first mentioned means;and

control means responsive to the size of the receiver member operative ona predetermined receiver member size to provide said control signalwhereby said uncharged strip is provided between the edge of saidreceiving member and the edge of said surface.

5. An electrostatic reproduction machine as defined in claim 4 whereinsaid means to provide an uncharged strip is adapted to provide theuncharged strip on either side portion of said photoconductive surface.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 09472 Dated May 7 1974 Invent Karl E. Liechty It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 6, claim 4, line 24, change 'to" (first occurrence) to on.

Signed and sealed this 24th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PO-1050 (10-69) USCOMM-DC wan-Poo 9 Us, GOVERNMENT PRINTINGOFFICE HID 0-366-334,

1. In an electrostatic reproduction machine having a movingphotoconductive surface adapted to be charged and to carry anelectrostatic latent image thereon, and developing means positioned at adevelopment zone to develop the moving electrostatic image on saidsurface, the developed image being adapted for transfer to a suitablereceiving member, the combination comprising: a discharge device adaptedwhen activated to discharge a charged area on a side portion of saidsurface, said device being positioned to discharge portions of saidsurface prior to development thereof; means adapted on a control signalto actuate said discharge device; and control means responsive to thesize of the receiving member operative on a predetermined receivingmember size to provide said control signal whereby said discharge deviceis activated to remove the charge on the side portion of said surfaceextending beyond the edges of said receiving member.
 2. In theelectrostatic reproduction machine as defined in claim 1 wherein saiddevice discharges charged areas on either side portions of saidphotoconductive surface.
 3. The electrostatic reproduction machine asdefined in claim 1 wherein said discharge means is a fluorescent lamp.4. In an electrostatic reproduction machine having a movingphotoconductive surface adapted to be charged and to carry anelectrostatic latent image thereon, and developing means positioned at adevelopment zone to develop the moving electrostatic image on saidsurface, the developed image being adapted for transfer to a suitablereceiver member, the combination comprising: means to provide anuncharged strip along the edge portion of said surface prior todevelopment thereof; means adapted to a control signal to actuate saidfirst mentioned means; and control means responsive to the size of thereceiver member operative on a predetermined receiver member size toprovide said control signal whereby said uncharged strip is providedbetween the edge of said receiving member and the edge of said surface.5. An electrostatic reproduction machine as defined in claim 4 whereinsaid means to provide an uncharged strip is adapted to provide theuncharged strip on either side portion of said photoconductive surface.